This article is a great discussion of modern imaging technology and I 100% agree that MRI is incredible. But CT has become much more impressive than the single-slice scanners of yore.
Watch this video of a modern scanner rotating at full speed:
http://www.youtube.com/watch?v=CWnjqeB7Mk8
Currently, the race to improvement is about speed and lower radiation dose. The newest scanners can take hundreds of 2D slices in a single rotation of less than a second and reconstruct the image with a huge variety of algorithms accounting for body part, patient size, etc. that all allow for lower dose and noise resulting in better diagnostic quality.
MRI is truly the cutting edge of human achievement. Watch this video to see the forces involved:
http://www.youtube.com/watch?v=6BBx8BwLhqg
And this for a detailed explanation of MRI principles:
http://www.youtube.com/watch?v=pGcZvSG805Y
Medicine uses 1.5T and 3T routinely for imaging, but higher field strengths are in use for research purposes. Innovation lately has been about developing new sequences (ways to differentiate types of tissue), and increase speed of aquisiton and comfort.
My doctor told me to have a CT scan done but I am worried about the radiation. I feel that if an MRI was cheaper, then I would have been prescribed an MRI.
CT is basically xrays in the round. You'll nominally use a radon transform (the actual approach is usually a back projection algorithm) to reproduce 3D position from a number of individual images. There are many good properties of this, it is relatively fast and cheap, it has very good spatial accuracy (e.g. a distance you measure on the image corresponds to a distance in the subject), but you have very little flexibility with tissue contrast. If an x-ray won't differentiate the features you are looking for, mostly you can only hope to add a contrast agent (typically expensive, fiddly, and more dose) where that is applicable.
By comparison, an MRI is more of a programmable imaging machine. You can get a lot of different contrasts by use of different pulse sequences, so you may be able to see features that are completely invisible in CT. On top of that, you can do interesting things with the time dimension and how things are changing while you image. This leads to approaches like functional MRI mapping which most people have heard of, but also diffusion and perfusion imaging. This can give you an idea of what is happening functionally, particularly in the brain. Downsides: time consuming (hence expensive), poor spatial accuracy, artifacts.
So for diagnostics or surgical planning, you get a lot more information from an MRI, but this also can take a lot more effort to interpret and understand.
While all those things (+ personnel costs) are of course worth paying for, I find it unbelievable that a simple scan could cost $5000 in the US! When I had to get a CT scan, it cost $2000, of which 90% was covered by the mandatory minimum health insurance. Nobody gets left out in the cold.
In France that would be closer to $100,000 (70k euros) typically.
MRI is a classic example of high fixed cost, negligible variable cost. Once they buy the machine, it pays to make sure it never runs idle.
This is only one example of how the medical industry has been ripping Americans off. And, before you say anything, PPACA does nothing to bring this system under control; in fact, it perpetuates and extends it.
http://www.osirix-viewer.com/Downloads.html OsiriX is a DICOM viewer and PACS for Macs and iOS
http://www.dcm4che.org/ dcm4che is a collection of server based applications for DICOM and PACS. Sort of like OsiriX, but web based. It's Java Tomcat based and reasonably simple to setup.
This is a cross platform viewer that is fairly capable (although very limited in 3D) and has some dicom communication capability.
We're currently in private beta. If interested, I'd be happy to hook up HN friends. Contact info in profile.
[1] http://dicom.offis.de/dcmtk.php.en
...and BTW, is anyone going to point out the obvious hazards of DIY x-ray dosing? Like, okay, sure, you can perform CT scans on inanimate objects in the privacy of your own home, without subjecting living creatures to x-rays, but still... open source x-ray machines?
Consider the infamous Therac-25:
The type that is used in clipboard backers is NOT good for laser cutting. Although it is also called MDF, it is dark brown, sometimes semi-gloss on the surface, heavier, and more structural. Unfortunately, the glue used to bond and seal it soaks up laser cutting energy and makes it very difficult to cut without significant char.
If you're looking for small amounts of laserable material for testing, laserbits is not a bad source (http://www.laserbits.com/index.php?main_page=index&cPath=82_...). However, in general I would recommend finding it locally at a lumberyard or home improvement shop as the quantity and pricing are better, and they will typically also cut it for you for a low price. Another source for this kind of material (at least in the US) are university bookstores, who havea (expensive) supplies for architecture majors.
A simpler approach to get a small CT scanner is to use a stationary source and detector. This requires a cone-beam source, which might cost a lot more, but it makes it a lot easier to experiment with phase-contrast and darkfield imaging, which can improve soft-tissue contrast.
For reconstruction from the projections the Cph CT Toolbox https://code.google.com/p/cphcttoolbox/ contains open source implementations of several reconstruction algorithms. It is written in python.
From my viewpoint, CS student focusing on medical imaging, no single imaging modality will rule them all. It is much more interesting to look at the combinations like PET/CT and PET/MR that gives us complimentary information.
Would have required an awful lot of scanning of xray film and would probably only have been able to image something around the size of a walnut.
Thank you for doing this. It's easy to build something cool but extremely unsafe in your home, forgetting that medical devices are carefully controlled to ensure patient safety. All it takes is one irresponsible DIYer to cause problems for everyone.
Frog levitating in 10 Tesla
